Overuse is to blame for arm injuries among youth baseball players, but
throwing curve balls at an early age still increases risk, according to a new report by
researchers at the University of North Carolina.1

Key findings

Pitchers with a previous history of injury are at 5 times greater risk of elbow and shoulder injuries, which the study attributed to inadequate rest, medical treatment, and recovery time after an initial arm injury;

The average number of innings pitched per game is a risk factor for shoulder injury in youth baseball pitchers;

Pitching in travel ball "elite" or "select" programs, and pitching in "showcase" events, were associated with increased risk of elbow and shoulder injury for those who also pitched in Little League Baseball and among high school pitchers;

The number of pitching-related injuries doubled between Little League (ages 8- to 13) and high school, mostly due to the higher number of innings[2] and pitches thrown; and

The relationship between age, type of pitch, and injury risk is complex, but researchers found "no
clear evidence"[3] that throwing breaking pitches at an early age was as
much an injury risk factor as innings pitched or previous history of
shoulder or arm injuries.

Travel ball increase overuse injuries

The study was critical of travel ball.

"The creation and evolution of 'elite' or 'select' baseball teams and leagues, if coupled with little or no regulation or regard for the health of the adolescent athlete, has the potential to increase the risk of invasive treatment and/or surgery [e.g. Tommy John surgery[4]], once reserved for adults," the study states.

Nearly one fourth of youth pitchers threw on travel ball teams and in Little League at the same time;

"Explaining to coaches, parents and players the high risk and limited reward of travel ball and showcases [is] high on the list," says the report, of ways to reduce the risk of pitching injuries.

End to curveball debate?

The Little League report, as well as articles in the media since its release, appear to downplay the injury risk from curveballs, but a close look at the study reveals no categorical statement that throwing curve balls at an early age is not an injury risk factor; it says only that "baseline risk factors for injury to Little League-age pitchers did not point directly to throwing curveballs."

Indeed, the very next sentence in the report - that children who pitched a higher number of innings pitched and had a previous history of shoulder or arm injuries "all were at higher risk for suffering arm injuries" - suggests that throwing curve balls isstill a risk, not just among the those factors that place youth pitchers at the highest risk.

Likewise, a chart included with the study, shows that throwing a slider was second only to pitching after a prior shoulder injury in terms of increasing the injury risk, with throwing curve balls at an older age in practice, throwing curve balls at an older age in games, and throwing curve in general all increased injury risk to varying degrees. The finding that a slider was second only to previous shoulder injury as a risk factor is consistent with earlier biomechanical studies reporting that throwing the pitch places more strain

Perhaps this is why the Little League press release accompanying the report is not only carefully worded on the subject of curveballs but takes pains to emphasize the practical difficulties Little League would encounter in enforcing any curveball ban.

"Some within the baseball community have advocated for a ban on curveballs," Stephen D. Keener, President and Chief Executive Officer for Little League Baseball and Softball, said. "However, the study conclusions do not clearly support such a ban."

"Furthermore, a ban on breaking balls would not be simple to put into practice," Mr. Keener said in the Little League statement. "With such a range of aptitude and ability, it's practically impossible to judge if any youth pitcher intended to throw a curveball or if that's just how the ball came out of the pitcher's hand. To task our dedicated volunteers with judging the type of pitch thrown is not only unfair, it would be impractical."

"Even if Little League were to find a practical way to ban curveballs in
our program, they would remain a part of the game for children playing
outside our program, as they have been for decades," Mr. Keener, a
Little League graduate, said. "For coaches and parents, armed with the
information in this report, the decision on when and how to teach the
curveball is a matter of preference and education."

The new report appears consistent with a 2010 ASMI study2 which attempted to study the risk of serious injury from throwing curveballs before age 13. But, while that study, like the new one, seemed to show a slight increased risk associated with starting curveballs at a young age, it had far too few participants to determine such an association. Thus, the authors, including Drs. Glenn Fleiseg and James Andrews of the American Sports Medicine Institute, concluded that the true risk of serious injury from starting to throw curveballs at an early age was, despite years of study, still unknown. Nevertheless, commenting on that study, and earlier studies,3, 4, 5, 6, Dr. Fleisig told the New York Times in 2009, that he didn't "think throwing curveballs at any age is the factor that is going to lead to an injury." 7

As for the Little Study, Dr. Fleiseg noted that, "Part of the confusion is that the pitchers that throw
curveballs tend to be the ones that throw a lot. So it's hard to
separate those factors. But when you do separate them statistically,
the pitchers who pitch too mucy are the ones who get hurt, whether they
throw a curveball or not."

Chicken or egg?

John Pinkman, the head of Pinkman Baseball Academy in Herndon, Virginia and MomsTeam's baseball expert, agrees with Dr. Fleiseg, noting that, "as a superior pitcher increases his pitch count, it is likely that he would increase the number of curve balls thrown. While confusing semantics is always involved in throwing pitches that go crooked, as opposed to those that go straight, young pitchers are often injured due to irresponsible training and attempts to force them to use competitive skills that are more suited for older players.

In practical application, due to the small hand of a child, to make a ball spin at the proper axis of rotation to create the traditional interpretation of a curve ball, the player must forcefully twist his hand, and subsequently his elbow, in a supinated direction (counter clockwise on a right hand thrower). Through overuse, that motion can and, very often has, caused serious repetitive micro trauma (in layman's terms, a sore arm). Medical professionals call it a 'door knob curve,' since the motion mimics someone opening a door."

As an expert on the mechanics of pitching, Pinkman notes that, "much less discussed is the fact that many players throw fast balls with a similarly excessive and premature supination. Routinely, we clearly observe this motion in our video analysis at very slow motion (480 frames per second). This type of pitch, although nominally a fastball, also increases the risk of overuse injuries because the ball is thrown with excessive force and more often. In the final analysis. proper training which takes into account the player's size, age and experience is the safest policy."

As Pinkman notes, "a really good pitcher, even at the elite level, strikes out about one batter per inning on average. The remaining 66% of the outs are grounders and fly balls. In my view, far too much emphasis is placed on curve balls at an early age to increase the number of strike outs."

Prevention strategies

Regardless of whether the Little League study puts to rest the controversy over curve and other kinds of breaking balls, it is valuable in correctly focusing attention on overuse injuries as the primary cause of arm injuries to youth baseball pitchers, identifying mandatory pitch count limits as the best prevention technique and in laying some of the blame for the increase in pitching injuries at the youth level at the feet of travel ball and showcases (which have not, until now, imposed pitch limits), and in viewing it as perhaps the biggest obstacle to injury prevention.

Properly stretching, warming-up[8], and cooling-down for pitchers, regardless of age.

Use common sense

"The practical implication [of the new study]," says ASMI's Dr. Fleiseg, "is that years of scientific study - from motion analysis in the lab to following kids on the field - support the fact that the best computer is right there on the field, in the player's head! If a pitcher is tired[9], he should stop pitching until the day he is fully recovered. If a pitcher has elbow or shoulder pain[10], shut him down until he sees a sports medicine specialist. The adults need to use "the computers in their heads" too. The coaches and parents need to be able to read the signs, and react when the player is fatigued or hurt. The data shows that following this common sense will maximize the chance for long-term success, whereas ignoring the signs will most likely lead to injury," says Fleiseg.

Study methodology

The study used three different test groups - Little League pitchers (ages 8-13); high school-aged pitchers; and college-aged pitchers. The Little League test group consisted of 410 players who were followed for four years between 2006 and 2010. The test group from the high school level was made up of 293 players who were recruited in 2007 and followed for additional years. The college test group consisted of 629 players that were followed for two years beginning in 2008.

The pitchers were surveyed each year to assess their pitching methods, techniques, pain presence and injury occurrence. The factors acquired from the surveys were then analyzed to assess which of those factors influenced pitching injury risk.

The study was commissioned by Little League Baseball and funded with a grant from the Yawkey Foundation.

UPDATE: USA Baseball and MLB's Pitch Smart program recommends that pitchers under the age of 13 avoid throwing pitches other than fastballs and change-ups, and that for pitchers ages 13 and up "can begin using breaking pitches after developing [a] consistent fastballs and change-up."

*In 2008, Little League Baseball became the first national youth baseball
organization to adopt the pitch count, instead of the number of innings
pitched, as the basis for its pitching rules. For more on its pitch count and mandatory rest rules, click here[1].

1. The Learning Curve: Little League Seeks to Address Concerns, Answer Questions about Curveballs & Overuse (Little League International 2011).